Arborvitae still top evergreen hedge choice

KENNEWICK -- Arborvitae is unarguably the shrub most commonly used to create an evergreen hedge, here and around the country.

Gardeners who are tired of seeing arborvitae used over and over again for hedges often ask me for a comparable substitute.

There isn't one. Arborvitae are the mainstay of evergreen hedges because they are perfect for creating a "green" fence or boundary.

Arborvitae are a dense evergreen shrub with a long life. They have no serious insect pest problems in our area, as well as no common leaf diseases or blights. They are tolerant of our local alkaline soils and don't have any difficulty enduring our scorching summer or cold winter conditions. Their one drawback is that they are subject to root rot if planted too deep or in poorly drained sites. Root rot also can be a serious problem if overwatered.

As a testament to their longevity, a drive around older areas of the Tri-Cities reveals how well arborvitae do in our area. However, you also might note just how big arborvitae can get. The species form of the eastern arborvitae (Thuja occidentalis), also known as the American arborvitae, can grow to a height of 60 feet and a spread of 10 to 15 feet.

Sixty feet is tall! No wonder people feel a need to chop them back when they get "too tall."

When those big old arborvitae originally were planted more than 20 or 30 years ago, there probably wasn't much of a choice of cultivars. Many planted the species form to create hedges.

Today, nurseries sell a variety of arborvitae cultivars with different mature sizes, shapes and even foliage colors. If you are considering planting an arborvitae hedge, check out the different cultivars available from your local nursery or nursery catalogs.

Here are just a few of the popular ones:

Pyrimidalis -- Smaller than the species, this cultivar still reaches a fairly lofty height, growing 20 to 30 feet tall and 5 feet wide. Without shearing, it has a formal outline with bright green leaves that turn bronzy in the fall and winter.

Emerald Green (aka Smaragd) -- Introduced in 1950, this cultivar has been around for a while. It has a narrow pyramidal form and grows to a height of 10 to 15 feet and a width of 5 feet, making it much smaller than the species. It has both good hardiness and heat tolerance.

Degroot's Spire -- This cultivar is a narrow columnar form growing 10 to 12 feet tall and 3 to 5 feet wide. The branchlets are spirally arranged giving the plant a natural spiral form. Foliage turns bronzy-purple during the winter.

Holmstrup -- Holmstrup also has been around since the 1950s. It has a compact, slow-growing conical form with a narrow, pyramidal shape growing to 5 to 10 feet tall and 2 feet wide. It stays dark green all year and is very hardy. ('Miky' is a cute little sport of 'Holmstrup' that's shorter and even more compact.)

Techny -- This slow-growing arborvitae has a broad-based pyramidal form and grows to 10 to 15 feet tall and 6 to 8 feet wide at the base. It has dense, dark green leaves all year.

So if you are thinking about planting an evergreen hedge, look for an arborvitae cultivar that is the size and shape you need, so you won't be enslaved with regular shearing of your hedge. I have listed only some of the popular cultivars. Check with your local nursery to find out what different ones they have available.

* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension.

This story was originally published April 2, 2011 at 3:00 AM with the headline "Arborvitae still top evergreen hedge choice."